The brain is an incredibly complex organ with many signals and chemical interactions taking place at any given time. Most commonly, the brain is involved in the control of the functions of the associated body. As such, the brain can be considered to interface with the body and actions associated with the brain are expressed by the body. Research has been done with the brain to determine the nature of the brain's control over the body and efforts have been made to interpret the signals in the brain with the hopes of controlling functions outside of the body. To this end, brain computer interfaces have been postulated.
A brain computer interface is an interface which receives information originating in the brain and transforms it into computer commands. A further definition may be an interface that accepts voluntary commands from the brain of a patient or specimen without requiring muscle movement. Brain computer interfaces have been the subject of several studies with mixed results. Early attempts at brain computer interfaces have included invasive methods of capturing voluntary signals from the brain of a specimen or patient. For example, electrodes have been placed in activity centers in the brain and based on that activity, computers or other devices have monitored those signals. Those signals can be converted into controls for computing devices. Invasive methods, however, have many shortcomings because they involve complex surgery or may otherwise pose unacceptable risk. In addition, these invasive methods tend to be incorporated into many single unit recording devices such as Electrocortincography.
Other invasive methods include, for example Positron Emission Tomography, where radioactive tracing elements are inserted into the blood stream of a patient. The gamma radiation emanating from the radioactive material may provide an image of the brain and may be used in one or more ways to measure brain activity and receive signals.
Non-invasive methods of measuring brain activity have also been considered. For example, Electroencephalography (EEG) provides several electrodes on the scalp of an individual and the summation of the firing of many neurons in the brain may be detected by the EEG.
More recently, the use of near infrared spectroscopy has been considered as a non-invasive way to measure brain activation. Near infrared spectroscopy has been used in human brain activation studies as a method for non-invasively assessing oxygenation changes in the brain. A light source emitting at least in part in the near infrared rang of the electromagnetic spectrum is positioned on the scalp of a patient and the photons that enter the tissue are either absorbed or scattered. A detector monitors the tissue. A percentage of the photons follow a relatively well-described pathway back to the surface of the scalp, where they can be measured with the detector. Different types of tissue and associated attributes of the tissue may cause changes in the absorption and/or scattering of the photons as they pass through the tissue. This technique allows calculation of changes in the oxyhemoglobin and deoxyhemoglobin rates in the tissue, which makes functional neuroimaging possible based on the information received at the detector.
Brain activity measurement has been considered for use as a controller of devices. However, the studies in this area have focused on, for example, Broca's region (a language processing region of the brain), providing a binary option for controlling a computer based on the word ‘yes’ vs. the word ‘no.’ In such an example, control of a computing device may be related to brain activity, but the activity is intended to control language, and is picked off in an ancillary manner and applied to computing.